The disclosure relates to gas turbine engines. More particularly, the disclosure relates to lubrication of fan drive gear systems in gas turbine engines.
Typical gas turbine engines have one or more turbine sections driving one or more compressor sections. The one or more turbine sections may also drive a fan. Many engines have an equal number of turbine and compressor sections (typically two). An exemplary such engine involves a low pressure turbine (LPT) section coupled to a low pressure compressor (LPC) section to drive the low pressure compressor section. Similarly, a high pressure turbine (HPT) section is coupled to a high pressure compressor (HPC) section to drive the high pressure compressor. In such situations, the fan is typically driven by the LPT. The rotating components of the LPT and LPC are commonly designated a low pressure spool while the rotating components of the HPT and HPC are commonly designated a high pressure spool. In such or other engines, the fan may be driven via a transmission (typically a gear reduction so that the fan is driven at a lower rotational speed than its driving spool).
An exemplary transmission is a fan drive gear system (FDGS) formed as an epicyclic geared transmission. With a typical fan at the front of an engine, the transmission is typically positioned between the fan and the LPC.
For lubricating the transmission, one or more supply pumps supply lubricating liquid (e.g., oil) to the fan drive gear system and one or more scavenge pumps typically scavenge the lubricating liquid from the fan drive gear system. If the scavenged lubricating liquid is highly aerated, a small scavenge pump may not be suitable to scavenge the lubricating liquid from the fan drive gear system, thus causing flow to back up and potentially lead to oil leakage, excess heat generation, and low oil quantity alarms. If a larger scavenge pump is used, that can add weight and take additional space, which is undesirable in systems where weight and space are a premium.
Exemplary lubrication systems, components, and methods of use are disclosed in US Pregrant Publications: 2008/0116010A1 entitled “Lubrication System with Tolerance for Reduced Gravity”; 2010/0212281A1 entitled “Auxiliary Pump System for Fan Drive Gear System”; 2010/0294597A1 entitled “Windmill and Zero Gravity Lubrication System”; 2010/0294371A1 entitled “Gravity Operated Valve”; and 2011/0108360A1 entitled “Oil Capture and Bypass System”; and 2008/0116009A1 entitled “Lubrication System With Extended Emergency Operability”; and U.S. Ser. No. 13/165,967, filed Jun. 22, 2011 entitled “Oil Bypass Channel Deaerator for a Geared Turbofan Engine”. The foregoing publications and application are incorporated by reference in their entireties herein as if set forth at length.